Caption: Cacti. Unidentified cacti (family Cactaceae) in a desert. Cacti are succulent plants, which means that they are able to store water in swollen tissues, enabling them to survive in arid desert regions. Their spines are modified leaves that protect them from herbivores and reduce the moisture loss that occurs through normal leaves. Photographed in the Atacama desert, northern Chile, one of the driest regions on Earth.